[AAVSO-HEN] GRB 070810B: XRT refined analysis

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
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TITLE:   GCN CIRCULAR
NUMBER:  6754
SUBJECT: GRB 070810B: XRT refined analysis
DATE:    07/08/11 01:59:15 GMT
FROM:    Rhaana Starling at U of Leicester  <rlcs1 at star.le.ac.uk>

R. Starling (U. Leicester), C. Markwardt (CRESST/GSFC/UMD) and F.E. 
Marshall (NASA/GSFC) report, on behalf of the Swift XRT team:

We have analysed 7.2 ks of Swift XRT photon counting mode data, beginning 
70 s and ending 13.8 ks after the BAT trigger, for the short GRB 070810B 
(trigger=287409; Marshall et al., GCN Circ. 6743).
We do not detect any X-ray sources at 3-sigma significance or greater 
within the refined BAT error circle (Sakamoto et al., GCN Circ. 6753).

Two low significance (2-sigma) possible sources are found within the BAT 
refined error circle at the following positions:

Source 1
RA (J2000)  =  00h 35m 51.2s 
Dec (J2000) = +08d 51' 21.3''

Source 2
RA (J2000)  =  00h 35m 50.0s
Dec (J2000) = +08d 48' 45.0''

Using the Bayesian method we find that both sources have between 4 and 26 
counts at the 99% confidence level.
It is not possible to determine at this stage whether or not either of 
these sources are fading.

We note that Source 2 lies 1.1 arcmin from the galaxy 2MASX 
J00355339+0849273 (= LEDA 1354367; RA, Dec (J2000) = 00h 35m 53.39s, 
+08d 49' 27.3''), which has angular diameter approximately 0.7 x 0.3 arcmin.

This is an official product of the Swift XRT team.